Usage of the word 用

Question

So I was watching a show and they say, 你不用留爸爸

And I got confused as to why they used 用 in it.

Is it the same when you don't use 用 in that sentence? Like,

你不留爸爸

Answer 1

你不用留爸爸 means "you don't need to/have to try to make dad stay" 你不留爸爸 would mean "you don't try to make dad stay", so more like stating a fact.